The present invention is directed to a bicycle shift control device which operates a shifting mechanism via a shift control cable, and specifically concerns a device in which a take-up body that takes up the shift control cable is caused to rotate in the take-up direction by means of a first shift lever which freely returns to a home position, and is caused to rotate in the pay-out direction by means of a second shift lever which freely returns to a separate home position.
A bicycle shift control device of the type noted above for operating a shifting mechanism via a shift control cable is disclosed in U.S. Pat. No. 5,921,138. The shift control device includes a control body for mounting to a bicycle in close proximity to a handlebar for controlling a pulling and releasing of the shift control cable. A first lever is mounted to the control body for movement which causes the control body to effect pulling of the shift control cable, and a second lever is mounted to the control body for movement which causes the control body to effect releasing of the shift control cable. One lever is pivotally coupled to the control body, and the other lever is coupled for linear movement relative to the control body. The lever structured for linear movement is coupled to a transmission mechanism for operating the control body in such a way that very little linear movement is needed to operate the control body. The transmission mechanism includes a plurality of ratchet teeth disposed in a common plane, wherein the path of movement of the linear operating body is parallel to the plane of the ratchet teeth.
Since the linearly moving lever moves in a direction perpendicular to the handlebar, for optimum operation the rider must position his or her thumb directly in front of the linearly operating lever and press the lever in the direction perpendicular to the handlebar. However, during competitive riding the rider usually does not want to worry about having to precisely position the thumb to operate the shifting device. Thus, it is desirable to have a shift control device of the kind noted above wherein the rider does not have to precisely position the thumb in front of the linearly operating lever for optimum operation.